This invention pertains to valves, and particularly to an improvement in the type of valve known as a Lunkenheimer valve. For a description of the Lunkenheimer valve see U.S. Pat. No. 2,996,075, the specification of which is incorporated herein by reference.
Such valves may be used wherever valves are required, but have proven especially useful in controlling the flow of caustic liquor in large diameter pipes in a Bayer plant where aluminum hydroxide is produced from bauxite.
The conventional Lunkenheimer valve has several shortcomings. One is that heretofore it has been manually controlled and has not been adapted to automated operation. Another is that, when used in a Bayer plant, it is subject to the buildup of scale from the caustic liquids passing through it. In the original Lunkenheimer valve, this scale can be removed only by taking the valve out of service.
While improvements in the Lunkenheimer valve have been made to make it self-cleaning, for example as shown in U.S. Pat. Nos. 4,177,825 and 4,338,961, the valves of these patents are relatively complicated. The present invention, on the other hand, provides a relatively simple mechanism for converting the original Lunkenheimer valve to a selfcleaning valve, while at the same time securing other advantages, as will become apparent from the following description.